1. Technical Field
The present invention relates to a method of preparing a haemostatic patch comprising a porous layer, for example a textile, based on oxidized cellulose and a film based on neutralized chitosan fixed on one of the faces of the porous layer.
2. Description of Related Art
Haemostatic patches are implantable medical devices for stopping the flow of biological fluids such as blood during surgery. For this purpose, they are generally composed of an absorbent porous layer, which is intended to trap the biological fluids, and a barrier known as a haemostatic barrier, which is intended to block the passage of the biological fluids.
Some haemostatic patches can be completely bioabsorbable, i.e. they are made to disappear in vivo after implantation, after a few weeks for example, when their function of stopping the effusion of biological fluids is no longer necessary.
Oxidized cellulose is of interest as a bioabsorbable material that can constitute the absorbent porous layer of a haemostatic patch: in fact, oxidized cellulose possesses intrinsic haemostatic properties.
Chitosan is a polysaccharide obtained by deacetylation of chitin. Chitin is one of the most widespread naturally occurring polysaccharides and is extracted from the exoskeletons of arthropods, from the endoskeletons of cephalopods as well as from fungi.
Chitosan has properties, such as biodegradability, bioabsorbability, biocompatibility, non-toxicity, and mechanical properties, that make it particularly interesting for medical applications. Thus, it would be interesting to combine a porous layer of oxidized cellulose with a film based on chitosan with a view to preparing a haemostatic patch. Chitosan in fact offers a good compromise, taking into account the properties that are required, for a haemostatic barrier, namely good biocompatibility and good mechanical properties.
However, chitosan is generally soluble in an acid environment. Thus, the films obtained from acid solutions based on chitosan are still highly laden with salts and still have their acid character. A chitosan film obtained from an acidic solution of chitosan can thus degrade and disintegrate when it is brought in contact with water or biological fluids. Therefore it can no longer perform its function of haemostatic barrier.
Accordingly, in order to be used in medical devices, especially in haemostatic patches, chitosan films must be neutralized. Generally this neutralization is obtained by treating these films with a strong base such as sodium hydroxide.
However, this treatment with sodium hydroxide can affect the integrity of the part of the patch supporting the chitosan film: thus, in the case of a haemostatic patch with an absorbent porous layer based on oxidized cellulose, treatment of the chitosan barrier film with sodium hydroxide would destroy the porous layer of oxidized cellulose.
Thus, it would be desirable to employ a method of preparing a haemostatic patch comprising a porous layer based on oxidized cellulose and a barrier film based on chitosan, which would avoid the phenomenon of degradation of the porous layer during the necessary neutralization of the chitosan film.